Field of Invention
The present invention relates to methods and compositions for increasing production of fatty acids in genetically altered sugar beet, other root crops, and/or Nicotiana spp. More specifically, the present invention relates to genetically altered sugar beet, other root crops, and/or Nicotiana spp. plants that express increased levels of one or more transcription factors and/or diacylglycerol O-acyltransferase 1 to produce higher amounts of at least one fatty acids (compared to levels of the fatty acid(s) in wild-type/non-modified plants) which are useful as a feedstock for production of biofuels; and the methods of generating these genetically altered plants. These genetically altered plants also have enhanced resistance to insects that feed on the genetically altered plant.
Brief Description of the Prior Art
Global warming, fossil fuel depletion, and the growth of worldwide energy consumption are major issues facing the 21st century. Governments and companies worldwide have been searching for solutions to these problems, in particular searching for approaches to increasing production of alternative fuels. Using corn to produce ethanol is one approach to producing an alternative fuel. Another method uses enzymes to increase the breakdown of cellulose for conversion to ethanol.
Currently, crops cannot be used to produce sufficient fuel to meet the increasing worldwide demand because of a lack of optimization for fuel production. For example, corn ethanol uses a small fraction of the total corn plant mass for fuel, and significant energy losses are incurred by the fermentation and distillation processes. In contrast, plant fats (also referred to as oils, fatty acids, and/or lipids) are chemically much more similar to crude oil. Most plant fats are long chain hydrocarbons (approximately 16 carbons) with a carboxylic acid group at one end. A primary difference between plant hydrocarbons and crude oil are the carboxylic acid groups present in plant hydrocarbons. Further, plant fats are already commercialized by the biodiesel industry which converts cooking oils (e.g., soybean, canola, sunflower, peanut) into fuel via chemistry. The cooking oils are fatty acids containing glycerin. The biodiesel processor performs a transesterification reaction which removes the glycerin and replaces it with an ethyl ester. These esters can be used instead of diesel fuel. However, the amount of hydrocarbons in various plants are not sufficiently high enough for commercially viable use of plant hydrocarbons as a complete replacement of fossil fuel hydrocarbons. Thus, a need exists for plants that can produce higher quantities of oils.
Interestingly, Andrianov, et al. (Plant Biotech. J. 8:277-287 (2010)) describes generating genetically altered Nicotiana tabacum cv. Wisconsin-38 and N. tabacum cv. NC-55 with DNA encoding Arabidopsis thaliana diacylglycerol O-acyltransferase 1 (Dgat or Tag1) under control of ribulose-1,5-bisphosphate carboxylase promoter (ssRBCS, a tissue-specific, inducible promoter) and with DNA encoding Arabidopsis thaliana leafy cotyledon 2 (Lec2) under control of AlcA, an inducible promoter. They then determined that these genetically altered plants produced higher amounts of fatty acids compared to wild-type plants (up to 5.6% fatty acids per dry biomass in their genetically altered tobacco compared to 2.8-4% fatty acids per dry biomass in wild-type plants). While the transgenic plants in Andrianov, et al. (2010) produced some higher levels of fatty acids (in particular, oleic acid), the genetically altered plants had dramatically lower amounts of linolenate acid compared to wild-type plants (from 67% of fatty acids in wild type plants to ˜35% of fatty acids in genetically altered tobacco plants). Linolenate acid is a major component of fatty acids in wild-type plants. In contrast to Andrianov, et al. (2010), the genetically altered plants described herein produce higher amounts of linolenic acid than achieved by Andrianov, et al. (2010), and higher percentage of fatty acids per dry biomass compared to Andrianov, et al. (2010); a surprising result. In addition, the genetically altered plants described herein also produced higher amounts of palmitic acid, linoleic acid, and palmitoleic acid than wild-type plants. Andrianov, et al. (2010) did not report the levels of palmitic acid, palmitoleic acid, nor linoleic acid produced by their N. tabacum plants transformed with either AtLec2 or AtTag1, possibly because their plants did not produce increased amounts of these fatty acids compared to the amount produced by wild-type plants.